1. Field of the Invention
This invention generally relates to a DC to DC regulator, and more particularly, to a system and method which is capable of converting a DC input voltage to multiple DC output voltages.
2. Description of the Related Art
In general, a DC to DC voltage regulator may be used to convert a DC input voltage to either a higher or a lower DC output voltage. DC to DC converters with step-up/step-down characteristics are often required in applications where the input voltage and the output voltage requirements are incompatible. For example, where an input voltage is 120 volts, a DC to DC converter may be required to step down the input voltage to a voltage level suitable for use by a particular system, such as, for example, down to 5 volts. Moreover, some operational systems may require multiple outputs voltages. Such applications may require a regulated power supply which is capable of providing output voltages of more than one value (e.g., a computer BUS system requiring xe2x88x9212, +12, xe2x88x925, +5 volts).
An example of a typical DC to DC voltage regulator which may be found in the prior art is disclosed in U.S. Pat. No. 5,436,818 issued Jul. 25, 1995 to Barthold (xe2x80x9cBartholdxe2x80x9d). Barthold purportedly discloses an improved regulator using at least two off-chip transformer components in an integrated buck-boost and buck converter system for eliminating the buck converter RHP zero effect characteristic. It should be noted, however, that where off-chip devices such as transformers are used, the off-chip devices necessarily increase the size and board space needed to implement the regulator design. Consequently, with the Barthold regulator, adequate space must be available to accommodate the bulk of the system transformers. This, in turn, results in a less space and cost efficient regulator device. As a result, recent regulator design efforts have focused on ways to implement a voltage regulator system while simultaneously reducing the number of off-chip devices employed.
With the above cost and space considerations in mind, more recent converter designs typically focus on switching regulators which minimize the use of transformers by primarily using integrated circuit technology (e.g., transistors, diodes, etc.) and passive electrical components (e.g., discrete storage inductors and filter capacitors). Typically, a switching regulator may control the voltage output by using one or more switches that are rapidly opened and closed to facilitate the transfer of energy between an inductor (a stand-alone inductor or a transformer, as examples) and an input voltage source. By regulating the voltage transfer in this way, the DC to DC switching regulator may control the value and position of the system DC voltage output.
One example in the prior art of a switching regulator using integrated circuit technology is the buck-boost switching regulator, described, for example, in U.S. Pat. No. 4,578,630 issued Mar. 25, 1986 to Grosch (xe2x80x9cGroschxe2x80x9d). Grosch purports to disclose a buck-boost switching regulator wherein separate signals are derived from a regulator output feedback signal for use individually in controlling the duty cycles of a multiplicity of regulator switches. Grosch further suggests variably controlling the regulator battery switch duty cycle and ground switch duty cycle so that at least one of the switches operates within a predetermined non-zero minimum duty cycle. In this way, Grosch purportedly uses multiple power switches in a design for converting a DC voltage input to a higher or lower DC voltage output.
One main drawback of the Grosch design is that the design requires additional circuitry which continues to consume valuable chip space. For example, in order to produce the separate signals derived from the regulator output, Grosch requires additional switching control circuitry for managing the maximum value of the voltage difference between the separate regulator signals. As can be understood, the additional circuitry continues to place certain cost and size limitations on the overall voltage regulator design.
Presently known DC to DC converters, therefore, remain inadequate, particularly in their ability to accommodate the trend toward producing smaller more cost efficient systems. Accordingly, an improved DC to DC converter circuit is needed which reduces the amount of off-chip devices (e.g., transformers, passive elements, etc.), as well as the amount of on chip circuitry used to generate the desired multiple output voltages. By reducing the amount of board space used, a voltage regulator designer may reduce the overall cost of a useful DC to DC converter system.
The present invention provides a DC to DC voltage regulator (e.g., converter) which addresses many of the shortcomings of the prior art. In accordance with various aspects of the present invention, a multiple output switching voltage regulator using a highly-efficient single power switching regulator with a single inductor and multiple regulated positive and negative outputs is provided. In accordance with one aspect of the present invention, the multiple output switching voltage regulator uses a voltage error signal to determine the sequence and/or priority of voltage output. That is, in one aspect of the present invention, the voltage output may be manipulated according to an error signal and the priority and sequence required at the voltage output.
In accordance With another exemplary embodiment of the system and method described herein, a voltage input is suitably connected to a current until the predetermined inductor current limit is reached. Control switches may then be used to provide the inductor current to a multiple of voltage outputs. The value of the voltage outputs is compared to a reference voltage for producing an error signal. The error signal is then provided to a decision logic block, which uses at least one of the inductor current value or error signal to determine the operational states of the control switches. The operational states of the control switches are determined such that the appropriate inductor current levels may be provided to the multiple voltage outputs, thereby controlling the order and priority of voltages output by the voltage regulation system.
In accordance with yet another aspect of the present invention, an inductor current is manipulated according to a error signal and the priority and sequence of the voltage regulator voltage output. In accordance with still another aspect of the present invention, the voltage regulator uses an inductor current to determine the sequence and/or priority of the voltage output.
In accordance with various other aspects of the present invention, a voltage regulator for generating multiple output voltages while reducing chip area by reducing the use of off-chip devices and/or circuitry is provided. In accordance with an exemplary embodiment, a voltage regulator is configured with a single power switch, single inductor element, error amplifiers, decision logic circuit (e.g. decision logic block), synchronous rectifiers or diodes, and switches. A predetermined inductor current value can be programmed into a decision logic block according to the requirements of the voltage output. The inductor current value may be further used to direct the inductor current to a specified voltage output. Moreover, an inductor current maximum value (e.g., an inductor current limit), may be programmed into the decision block for use in determining the maximum allowed value of the inductor current in the regulator, and for determining the priority and sequence for providing excess current to a voltage output.
In addition, an error signal can be generated based on the actual and desired voltage output, which may be used by the decision logic block to control the current provided to the voltage outputs by the inductor element. That is, the decision logic block may use the information provided by the error signal and inductor current to control the sequence and priority of switch operational modes which may be used to generate the desired voltage output.
Power switching regulator with single inductor and multiple regulated positive and/or negative outputs is provided, wherein the regulator includes an integrated circuit
In accordance with yet another exemplary embodiment of the present invention, a single power switching regulator with single inductor and multiple regulated positive and/or negative outputs is provided, wherein the regulator includes decision logic block for controlling the regulator output voltage priority and/or sequence.
In accordance with still another exemplary embodiment of the present invention, a single power switching regulator with single inductor and multiple regulated positive and/or negative outputs is provided, wherein the regulator uses a single inductor to provide current to the regulator outputs.
In another exemplary embodiment of the present invention, the inductor current is permitted to circulate throughout the voltage regulation system until called upon by the decision block to be provided to the voltage outputs.
In yet another exemplary embodiment of the present invention, the decision logic block may determine the state of the power switch and control switches, as well as, the inductor current to produce positive voltages, negative voltages or both.